Process for bleaching clay



July 6, 1965 J. IANNICELLI ETAL 3,193,344 PROCESS FOR BLEACHING' CLAY Filed March 26, 1962 WATER HSRCOOH 'x v z i I CLAY DEWATER FILTER AIR 3-: 2. I rWASTE Q. o. v t 7.. .Of T

x Fe S SEPARATE -X-- DRY PRODUCT INVENTORS JOSEPH IANNICELLI PETER ABOYTES United States Patent 3,193,344 PROCESS FOR BLEACHING CLAY Joseph Iannicclli and Peter Aboytes, Berger, Tex., assignors to J. M. Huber Corporation, Locust, N.J., a corpoice In the preferred process, the reaction of clay and these agents is carried on at a slight degree of acidity. The crude clays may thus be treated, without the production of objectionable amounts of fumes, to obtain a clay of fi f N W Jews 5 very greatly improved color. Any reducing agent active m on s Man 1962, SerNm 182,519 in the pH range of the liquor in which intended to be 7C1aims (CL used to reduce ferric compound to ferrous compounds may be used. In the preferred embodiment, because of T is invention relat s to tr at t fc y more economic considerations, water-soluble salts of hydrosulparticularly, to an improved process of bleaching clay with 10 phurous acid are preferably employed in the process of a novel combination of chemical treating agents. It is this i ti S lt hi h h proved to b i known that the whiteness of clay can be improved by lariy satisfactory for this purpose are sodium hydrosu1- various bleaching agents. The amounts and costs of the phite, zinc hydrosulphite, and calcium hydrosulphite. agents required depends, however, generally on the The amount of hydrosulphite is small, on the order of amount of impurity to be removed; accordingly, the treatless than 10 pounds per ton of clay, even when low color ment of low color clays has, to date, been prohibitively clays are used. Further, hydrosulphurous compounds, expensive. Such has hindered the economic value and such as taught in US. Patent 2,339,594, page 1, column development of such type of clays. 2, lines 32-54 may be also used; e.g., alkali metal and In the usual or conventional processes for brightening zinc salts of hydrosulphurous acids and the sulfoxylates. clays, iron compounds initially solubilized from the clay By sulfoxylates is meant the compounds formed by the remain in the aqueous portion of the clay slurry as simple reaction of aldehydes with metal salts of hydrosulphurous water-soluble salts. These have a tendency to be reacids; sodium hydrosulphite, zinc hydrosulphite, calcium adsorbed and remain with the clay product and produce, hydrosulphite and the corresponding salts of formaldeon drying, a clay of lower color. Such undesirable rehyde sulfoxylate and hydrazine are used. Such comsults are avoided according to the process of this invenpounds can be added in dry form or as aqueous solutions tion. thereof to the slurry of clay to be treated. In order to It is, accordingly, one object of this invention to proillustrate this invention more clearly, modes of carrying vide an improved process for the bleaching of clays the same into eliect and advantageous results obtained whereby a large improvement in the color of the clay thereby are given in the following examples; Examples is obtained. 1 through 0-6 are summarized in Table I.

TABLE I Treating composition and characteristics G.E. brightness Crude slip Ex. N0. Low color pH 1 high Suprex Other M 820 Alum M.A.A. Other pH Color of Feed Product Change color reagents liquor .5 0.3 0 0 LG. 70 79 +9 .5 0.3 2 0 70 86 15 .5 0.3 1 70 83 13 .5 0 0 72 80 s .5 0 2 70 81 11 .5 0 4 70 83.5 13.5 .5 0 5 70 85 15 .5 0.3 0 77 52 5 .5 0 5 77 83 c .3 0 2 77 82 5 1.0 0 0 77 82 5 .5 0.3 0 82 85.5 3.5 .5 0.3 2 s2 88 e .3 0.3 0 s5 88 2 .3 0.3 1 86 a0 4 0.5 0.3 0 82 86.5 4.5 0. 5 0. a 1. 0 s2 00. 3 +8.3

In% solid slurry. 2 Percent ofweight oisolid feed. Mercapto accticacid. Light green color. 5 Forth floated clays. Waterwash. Another object is to provide a process for improving TABLE II clays of low color which avoids the generation of objectionable fumes. High. Fractiom A further object of this invention is to provide a process Chamlenstlcs color Color SIIPWX 1 Med crude crude for whitening clay 1n a particularly economic fashion.

Still other objects of this invention will be apparent P t A] 0 39 39 to those skilled 111 the art on study of the disclosure hererii g t Sign?" 44 45 22.3 i; inbelowi fifi i $5 til 1'3; 1 58 *2 e n 1 The above and other ObjeClIS of this invention are acpH value n 5-5 6-7 4.5-5.5 4. 5-5. 0 complished by treating an aqueous slurry of the clay to fi i g f fjfffj f 6944 62458 8742 9H4 be bleached with a reducing agent and an iron binding Particle size, percent, +5 agent generally describable as a water-soluble polyfuncmicrons 8-11 1245 0-1 tional organic compound, one active group of which comprises a mercaptan (SH) radical and another active group of which comprises a radical capable together with the mercaptan group of chelating iron. The characteristics of such agents which, with iron, form a complex readily and conveniently separated from the particles of clay are described below in detail.

1 Registered trademark of .T.M. Huber Corporation. 3 As per part III, page 102 of Kaolin Clays and Their Industrial Uses J.M. Huber Corp., New York, 1955.

The product of Example A-3 gave the following analysis:

F6203 1.81% Ti0 2,400 grams of degritted low-color Georgia kaolin clay (G.E. brightness of 70 as measured at pages 96-79 of Kaolin Clays and Their Industrial Uses, J. M.. Huber Corporation, New York, 1955) of composition as in Table II was cut into eight equal portions. One 300-gram portion was mixed with 700 grams of water at 60 C. by a laboratory mixer in an open-topped upright cylindrical container open to the air and a uniform slurry was.

formed. The pH of this clay slurry was 5.7. Then 1.5

grams of sodium hydrosulfite and 0.9 gram of alum were .added thereto. Themixing was continued for 30 minutes at 60 C. as in United States Patent 2,339,594. The odor of this reaction mixture was strong but not objectionable.

.The stirring energy of the laboratory mixer was sufficient to keep-the clay particles in the reaction mixture suspended and agitated but insuificient to afiect the particle size of the clay feed. The clay and liquor were then separated by filtration in the air, the clay recovered and dried at 90 C. to a moisture content'of 1 and the GE. brightness determined as above.

The filtrate of the filtered reaction mixture was a liquor initially clear but it developed a definite turbidity and light green color as of ferrous hydroxide within a few minutes. This ,color gradually turnedin a period of .2 to 4 hours ,to the reddish brown color characteristic .of ferric hydroxide. I

laboratory filter paper provided thereon a reddish brown Filtration of this liquor through residue of hydrated ferric oxide. Data on this example are recorded in Table I as Example A-l. In Example A-2, a clay slurry was made up from second 300 gram portion of the clay feed used in Example A-l. This portion was mixed and heated as in Example A-1 except that 7.5 cc. of an 800-gram per liter aqueous solution of mercaptoacetic acid was added thereto. The GE. brightness of the clay product recovered and dried as in Example A-1 was determined as 86. The reaction mixture during the initial portion, as well as in the final portion of the 30-minutes reaction period, did not have an objectionable or strong odor although initially an in-this example was initially clear and colorless and remained so for a four-day period, far longer than the 2-4 hour period of time in which the filtrate of the reaction mixture in Example Al had become turbid and red colored. Data on this example are given as Example A-2 in Table I.

Example A-3 was parallel and identical to Examples A-2 and A-1 except that 3.75 cc. of the solution of mercaptoacetic acid was used; the pH of the reaction mixture of clay, treating agents, and water was 3.8. The reaction mixture, as in Example A-2, had an odor during the 30- minute reaction period that was observable but not objectionable. The filtrate of the reaction mixture was clear and colorless as in Example A2. The GE. brightness of the filtered clay product was 83 (determined as in Examples A-1 and A-2).

Example A-4 was run parallel and identical to Exam- 7 ple A 3 except that 30 grams of acetic 'acid as 50% solution was used (in place of the mercaptoacetic. acid and alum) on a low-color clay of initial GE. brightness of 72.

The GE. brightness of the filtered and driedclay product was 80. This test shows that even such an amount of acid as would be uneconomical to use does not, even in combination with an amount of sulfurous salt which produces a maximum brightening effect forsuch salt, produce an improvement eifect on brightening of clay as good as that produced by mercaptoacetic acid when used in amount odor was observable. The filtrate of the'rea'ction mixture the filtered and dried clay product was 81. The reaction mixture of clay and treating agents had an odor during the reaction period that was noticeable but neither objectionable nor strong.

Example A-6 was run parallel and identical to Example A-S except that 12 grams of mercaptoaceticwas used. The filtrate from the reaction mixture had no color and was clear; the reaction mixture had an odor, as in Example A5, that was noticeable but not objectionable or strong. The GE. brightness of the filtered and dried clay product was 83.5.

Test A-7 was run parallel and identical to Example A6 except that 15 grams of mercaptoacetio acid was used. The GE. brightness of the filtered and dried clay product was 8 5.0. The filtrate from the reaction mixture was clear and had'no color. The reaction mixture of clay and treating agents had an odor during the reaction period that was noticeable but neither objectionable nor strong, although the mercaptoacetic acid solution used had a strong but not objectionable odor as was also in the case of test A-6.

Examples B] through 84 'Suprex clay. (analysis given in Table II) having a GE.

brightness of 77 was admixed with 700 grams of water at 60 C., as in Example A-l. The pH of, the resultant slurry was 5.0. Sodium hydrosulfite and alum were added to the slurry and admixed therewith for 30 minutes. at 60 C., as in Example A-l. The pH of the resultant slurry was 4.2. Sodium hydrosulfite and alum were added to the slurry and admixed therewith for 30 minutes at 60 C. as in Example A-1.' The pH of the resultant reaction mixture was 4.7. The GE. brightness of the clay product (filtered, recovered and dried as in Example A-l) was 82. The filtrate from the reaction mixture was light green in color. The reaction mixture had no observable odor. Example B-2 was run parallel and identical to Example B-1 with another 300-gram portion from the 1200- gram sample used in Example B-l except that 15 grams of mercaptoacetic acid added as an 800 grams per liter aqueous solution, having a strong but not objectionable odor, was used in place of the alum. The reaction mixture had an observable, but not objectionable or strong,

V clay and treating agents had an observable but not obwith 700 grams of water at Chas in Example A-l.

jectionable or strong odor. The GE. brightness of the filtered, dried clay product was 82.

Example B-4 was run parallel to'and identical to Example B-l with another 3O0 gram sample, as in Example B-Z, except that no alum was used. The GE. brightness of the clay product was 82 I Examples C-1 through C4 In Example C-1, 300 grams of a 900-gram sampleof high color air floated Georgia kaolin clay.(analysis in Table II) having'a 'G.E. brightness of 82 was admixed The pH of the resulting slurry was 6.7. 1.5 grams of sodium hydrosulfite and 0.9' gram of alum were added to the slurry and admixed therewith for 30 minutes at 60 C. to form a reaction mixture in the same manner as in Example A-1. The G.E. brightness of the clay product was filtered, recovered, and dried as in Example A-1 and was 85.5. a

In Example C+2,'a second 300-gram portion of the 900- grarn' sample of high color clay used in Example C-l was treated parallel and identical to test C-l except that 6 grams of mercaptoacetic acid added as an 800 grams per liter aqueous solution was used, and zinc instead of sodium hydrosulfite was used. The filtrate from the reaction mixture was clear and had no color. The reaction mixture had an odor that was observable but not objectionable nor strong. The G.E. brightness of the clay produced was 88.

In Example C3, 300 grams of a 600-gram sample of high color clay produced by froth flotation and having a- GE. brightness of 86 was admixed with 700 grams of waterat 60 C. as a Test A-l. 0.9 gram of zinc hydrosulfite and 0.9 gram of alum were added to the slurry and admixed therewith for 30 minutes at 60 C. to form a reac-' tion mixture in the same manner as in Example A1. The filtrate from the reaction mixture had a light green color. The GE. brightness of the product was 88.0.

' In Example (3-4, the remaining 300-gram portion of the 900-grarn sample of high color clay used in Example Cl was treated parallel and identical to Example C3 except that 6 grams of mercaptoacetic acid was added as an 800 gram per liter aqueous solution, and zinc hydrosulfite was used. The filtrate from the reaction mixture was clear and had no color. The reaction mixture had an odor that was observable but not objectionable nor strong. The GE. brightness of the clay produced was 90.0.

\ In Example 05, 300 grams of a 600-gram sample of highcolor clay produced by water fractionation,analysesas in the Table II, and having a GE. brightness of 82 was admixed with 700 grams of water at 60 C. as in Test A-l. 1.5 grams of zinc hydrosulfite and 0.9 gram of alum were added to the slurry and admixed therewith for 30 minutes at 60 C. to form a reaction mixture in the same manner as in Example A-l. The filtrate from the reaction mixture had a very light green color. The GE. brightness of the product was 86.5.

In Example C6, the other SOD-gram portion of the 600- gram sample of high color water-fractionated clay used in Example C-S was treated parallel and identical toEX- ample C-S except that 3.0 grams of mercaptoacetic acid, added as an 800-gram per liter aqueous solution, was used in addition to the alum.

The filtrate from the reaction mixture was clear and had no color. The reaction mixture had an odor that was observable but not objectionable nor strong. The GE brightness of the clay produced was 90.3.

In yet another example, C7, of this invention a clay slurry was made up from a 300-grarn portion of the same clay feed (G.E. brightness of 70) used in Example A-1. This portion was mixed and heated as in Example A-l with 1.5 grams of zinc hydrosulfite and 0.9 gram of alum except that 3.75 cc. of an 800-gram per liter aqueous solution of thiomalic acid also was added thereto. The GE. brightness of the clayproduct recovered and dried as in Example A-l was determined as 85.5. The reaction mixture during the initial portion as well as in the final portion of the 30-minute reaction period did not have an objectionable or strong odor although initially an odor was observable. The filtrate of the reaction mixture in this example was initially clear and colorless and remained so for a period in excess of 24 hours.

Another example was run parallel and identical to Example C-7 except that 7.5 cc. of an aqueous solution of mercaptoethanol was used; the pH of the reaction mixture of clay, treating agents and Water was 3.8. The reaction mixture, as in Example A-Z, had an odor during the 30- minute reaction period that was observable but not objectionable. The filtrate of the reaction mixture was clear and colorless as in Example A-2. The GE. brightness of the filtered clay product was 85 .5.

In yet another procedure for improving the color of clays, the procedure of Example C7 was repeated on the same low color crude (G.E. brightness of 70) using 15 grams of hydroxyacetic acid (in a 70% aqueous solution) in place of the 3 grams of mercaptoacetic acid aqueous solution there used. The resulting clay product had a GE. brightness of 84.5. The procedure of Example C6 was repeated using the same water-washed clay (GE. brightnessof 82.0) and using 15 grams of hydroxyacetic acid in place of the 3 grams of mercaptoacetic acid used in that example. The GE. brightness of the product was 90.0.

After the bleaching operations as above described, the clay may be separated from the slip in any convenient manner and dried. The clay may be coagulated to improve its filtering characteristics.

It is, accordingly, seen that the process of this invention improves the color of high color clay crudes as Well as intermediate and low color clay crudes. Also, such results are obtained without development of objectionable amounts of fumes even while operating from 60 to C., notwithstanding the generally accepted malodorous characteristics of mercaptan reagents.

While not limiting the invention thereto, a theory of this invention, which is included within the scope of this invention, is that in conventional clay bleaching operations the reducing agentas sulfoxylates as above defined -reduces water-insoluble colored ferric compounds carried by the clay and forms therefrom water-soluble ferrous compounds. The thus-solubilized iron is then partially reoxidized by air while in aqueous solution (which solution is in contact with the clay particles of the reaction mixture) or in contact with solution in contact with air, thus forming water-insoluble colored iron compounds which are readsorbed on the clay and cannot thereafter be removed by washing. According to this invention, however, notwithstanding the presence of air and agitation of such solution with air, the solubilized ironcompounds produced as above described from the clay are brought into contact with an agent which forms a sufiie ciently stable combination therewith to prevent .reoxidation of that reduced iron and so stabilizes the scavenging of such iron theretofore effected from the clay by the reducing agent.

A sufficiently stable combination to prevent such reoxidation in aqueous solution exposed to air is effected by the reaction of such solubilized iron with a water dispersible agent containing a mercapto radical and a radical chosen from the group consisting of hydroxyl and carboxyl radicals. Preferably such agent is a watersoluble acid-herein referred to as dibasiccontaining a carboxyl and a mercaptan radical or group-preferably with the SH radical or group in the alpha position relative to the carboxyl radical or group, such as in mercaptoacet-ic acid; such a mercapto-carboxy acid forms in aqueous solution a water-soluble, preferably, or at least a water-dispersible compound or complex of sufiiciently slight degree of dissociation to prevent reaction of the iron and oxygen from the air in a reaction mixture such as in the above examples and so prevents oxidation and readsorption of said iron on the clay from which previously removed. The thus-held iron is readily removed from the clay, as by filtration. This admixture of such dibasic mercaptan acid and reducing sulfoxylate is effective at the relatively acid pH conditions at which such sulfoxylate is most effective to reduce iron compounds associated with even relatively acid reacting clays without producing an objectionable or strong odor.

Other acids and compounds which also form similarly water-soluble compounds with ferrous iron of sufliciently low degree of dissociation to prevent reoxidation of fer rous iron compounds to ferric iron compounds in presence of air, water, and clay as in the reaction mixtures of the examples above include thiomalic acid and mercaptoethanol. This is because it is within the scope of this invention that acids and salts producing water-soluble and water-dispersible iron compounds separable from clay and having a dissociation constant in the range of and less than that of the compounds formed by the anions of mercaptoacetic acid or thiomalic acid or mercaptoethal with ferrous iron, as in the complex formed therebetween in the above examples, may be used in 7 place of mercaptoacetic acid in the procedures described in the above examples.

This invention also provides for a'reclamation of the mercapto-carboxyl reagent and production of sulfoxy compounds at an extremely economic level useful in clay treatment as above whereby clay crudes of low, high, and intermediate color may be treated economically to improve their color. The overall process of this invention including this reclamation process is shown diagrammatically in FIGURE 1, which figure forms a part of this specification.v

As shown in FIGURE 1, separation of the liquor of the clay slurry from the clay during the recovery of the clay provides a liquor which may be treated-as by H S or Nags: or ammonia-to selectively precipitate the iron in a water-insoluble form as iron sulfide (Fe S or iron hydroxide and so regenerate the water-soluble iron complexing agent as mercapto-carboxy acid (shown generally as HSRCOOH). Further, after removal of the resulting insoluble iron sulfide precipitate from saidliqnor, as by filtration and/or centrifugation, controlledoxidation of the resulting liquor as shown diagrammatically in FIGURE 1 converts any undesired excess Na S or H 8 required for iron removal to a reducing sulfoxy compound such as sulfoxylates (shown generally as M S O and in the desired pH range. Such sulfoxy compounds, in combination with the reclaimed mercapto carboxy acid, such as mercapt'oacetic acid, may be used again for brightening further portion of clay in the manner described in the above examples, such as A-2, B-2,

and C-2.

The clay products ,of the process of this invention from which the iron has been scavenged, such as described in the above examples, are'entirely amenable to incorporation with conventional rubber compound mixtures. For example, 104 parts by weight of the treated clay of Example B-2 with 100 parts GRS rubber, parts zinc cal selected from the group consisting of carboxy and hydroxy radicals, and finally separating the iron complex from the clay.

2. Process of treating a first portion of clay containing colored water insoluble ferric iron compounds comprising the 'steps of addingto an aqueous slurry of said clay, a mixture of a mercapto-carboxy acid capable of forming a complex with ferrous iron and a reducing compound capable of reducing the ferric iron of the clay to ferrous iron, reacting said mixture with said clay, separating the clay from the liquor, and treating said liquor with more than the amount stoichiometric to the complexed iron of a compound capable of forming an insoluble iron compound selected fromthe group oxide, 3 parts sulfur, 2 parts accelerator (as N-cyclohexyl-Z-benzothiazole sulfenamide) and 8.5 parts of softener, as polymers of indene and coumarone, produce, on a 60 minute cure, mechanically useful'rubber compounds with strength characteristics of about 1700 p. s.i; tensile strength, 700% elongation, and a Goodrich tear test strength of 120 pounds per inch thickness.

The above invention is not to be considered as limited to the specific embodiments and theory disclosed as many variations and modifications of the process will be readily apparent to those skilled in the art, which modifications and variations are intended to be included within the scope of the appended claims.

We claim:

1. Process for the treatment of clay to improve the color thereof which comprises contacting; an aqueous suspension of the clay with a reducing compound capable of reducing the ferric iron impurities of the clay to ferrous iron and then adding a water soluble polyfunctional organic chelating agent capable of forming a complex with the ferrous iron, said complex being separable from the clay and said chelating agent containing as one'active radical, a mercapto group, and a second active radiconsisting of sodium sulfide, hydrogen sulfide, and am-- monia to separate allthe iron from the complexing compound thereby regenerating the mercapto carboxy acid and separating the insoluble iron compound from the liquor. r

3. A. process for the treatment of clay inan aqueous suspension to improve the color of the clay, first contacting'the aqueous suspension of the clay with a reducing compound capable of reducing the ferric iron impurities of the clay to ferrous iron and then adding a water soluble polyfunctional organic chelating agent capable of forming a complex with the ferrous iron, said complex being separable from the clay and having a dissociation constant no greater than the highest dissociation constant of a compound formed by the' reaction between ferrous iron and a member selected from the group consisting ofrmercaptoa'cetic acid, thiomalic acid, and mercaptoethanol, said chelating agent'containing asone active radical, a mercapto group and a second active radical selected from the group consisting of carboxy and hydroxy radicals, and finally separating the iron complex from the clay. a.

4. Process as in claim 1 wherein the agent is a watersoluble polybasic acid containing a carboxy group and mercapto group, one of said groups being in the alpha position with respect to the other. v

5. Process as in claim 4 wherein the agent is mercaptoacetic acid and the treatment is carried out at an acid pH.

6. Process as in claim 4 wherein the agent is thiomalic acid and the treatment is carried out at an acid pH.

7'. Process as in claim 4 wherein the agent is mercaptoethanol and the treatment'is carried out at an acid pH.

References Cited by the Examiner UNITED STATES PATENTS 1,588,956 6/26 Feldenheimer 23-1102 2,339,594 1/44 Williams 23-1102 :2,s39,595 1/44 Williams 23-110.2 2,500,727 3/50. Whittaker 23 110.2

' I FOREIGN PATENTS 7 2,309 1914 Great Britain.- 886,653 1/62 Great Britain.

MAURrcE A. BRINDISI; Primary Examiner. 

1. PROCESS FOR THE TREATMENT OF CLAY TO IMPROVE THE COLOR THEREOF WHICH COMPRISES CONTACTING AN AQUEOUS SUSPENSION OF THE CLAY WITH A REDUCING COMPOUND CAPABLE OF REDUCING THE FERRIC IRON IMPURITIES OF THE CLAY TO FERROUS IRON AND THEN ADDING A WATER SOLUBLE POLYFUNCTIONAL ORGANIC CHELATING AGENT CAPABLE OF FORMING A COMPLEX WITH THE FERROUS IRON, SAID COMPLEX BEING SEPARABLE FROM THE CLAY SAID CHELATING AGENT CONTAINING AS ONE ACTIVE RADICAL, A MERCAPTO GROUP, AND A SECOND ACTIVE RADICAL SELECTED FROM THE GROUP CONSISTING OF CARBOXY AND HYDROXY RADICALS, AND FINALLY SEPARATING THE IRON COMPLEX FROM THE CLAY. 